I had an Audiovox PPC-6700 for 6 months and used the Plantronics D-640 bluetooth flawlessy. The screen went out on the phone and the new PPC-6700 won't stay paired with the 640 for more than an hour. Sprint is telling me that this phone will not work with this particular bluetooth (although I have 4 friends with the same phone and bluetooth and they have no problems at all). Any ideas?